This invention relates to an air conditioning system for conditioning air in a plurality of areas or spaces in a common enclosure, and more particularly, relates to a control for regulating the operation of said system.
In recent years, many multi-zone buildings, such as schools, offices, apartments and hospitals, have employed central station air conditioning systems to provide conditioned air to regulate the psychometric properties of the air in each of the zones of the building. Very often, each of the spaces are divided into peripheral zones and interior zones. The interior zone of a space generally requires conditioned air at a constant relatively cold temperature to compensate for relatively constant heat producing sources, such as lights, machinery and people. Sometimes, the interior zone supply terminal is designed to deliver a sufficient quantity of relatively cold air so that the entire space may be cooled thereby even during summer conditions.
In such a system, the exterior zone of each space will only require means to provide relatively warm conditioned air during conditions, for example during the winter season, when heat generally flows from the building to the ambient. At times, during winter operation, when the temperature of the ambient is relatively low and there is no sunload to negate transmission losses, the continued discharge of conditioned cold air is entirely unnecessary and undesirable. However, at other times during winter operation, the presence of a sunload will prevent transmission losses of heat to the ambient, thereby requiring the continued discharge of the relatively cold air to compensate for the relatively constant heat producing means, such as lights, machinery, and people. During the latter condition, the continued discharge of relatively warm air is undesirable.
Heretofore, many of the aforedescribed systems have not provided control means to regulate the discharge of both conditioned air streams i.e. relatively warm and cold streams. Very often, only the cold air stream is under the control of quantity regulating means responsive to the temperature in the space. In order to conserve installation costs, designers and installers of systems of the type discussed, have assumed that once the ambient temperature declined to a relatively low level, for example below 50.degree. F, heat would always be required in the areas within the enclosure. Accordingly, when the sunload is relatively strong, even though the ambient temperature is below the setpoint for activation of the warm air supply means, both relatively warm and cold air streams would be simultaneously discharged. As is manifest, the foregoing is not desirable when the conservation of energy and the reduction of operating costs are wanted. Although the use of separate thermostats on the respective cold and warm air supply means might overcome the foregoing problem, this solution would result in an undesirable increase in the installation cost of the system. In addition, the use of two separate thermostats may result in the simultaneous discharge of both hot and cold air streams.
Some system designers have attempted to compensate for solar radiation by employing devices to sense solar rays. Such devices have not always proven to be reliable and in addition, such devices do not take into account the storage effect of the peripheral walls of the building. Thus, although there is always a time lag between the introduction or withdrawal of solar rays and the effect of such rays on transmission gains or losses, solar compensating devices do not take such delay into consideration. Accordingly, the actual requirements of an area or space may be somewhat different than the theoretical requirements as determined by the presence or absence of solar radiation. Furthermore, the use of solar compensators result in undesirable increases in the installation cost of the system.